GB2140223A - Electrical connection devices, for example mains plugs - Google Patents

Abstract

A connection device, such as a 13 Amp mains plug, has the following features: the connection elements (20) are equally spaced from the cable entry to facilitate preparation of the wires of the cable; the wires are fed through separate tunnels (38) to the connection elements (20) to reduce the risk of stray wire strands from different wires touching; the cable grip (36) comprises a resilient vane on the cover and/or base (10) of the plug which grips the cable when the plug cover is fitted to the base; and the tunnels (38) are colour-coded (at 40). Each connection element may comprise complementary, serrated clamp pads (20) on the cover and base which clamp the bare end of the wire when the cover is fitted to the base or may comprise conventional screw-clamping terminals. The cover may be secured to the base by a hook or hinge arrangement and screws. <IMAGE>

Description

SPECIFICATION Electrical connection devices, for example mains plugs The present inventions relate to electric connection devices of the type now defined as comprising an insulating base carrying conductor elements, an insulating cover adapted to fit the base and means to draw together and secure together the base and cover, as having a cable entry opening, and as further comprising means for electrically connecting conductor cores of the cable to respective ones of the conductor elements.

Examples of said devices are electrical plugs and sockets, mains spur outlets, and junction boxes.

In accordance with the present inventions, there are provided such devices as are claimed in the appended claims 1, 2, 3, 6 and 8, with preferred features of the inventions being defined in the remaining claims.

Specific embodiments of the present inventions will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is an enlarged plan view of a base of a three-pin 13 Amp mains plug; Figure 2 is a sectional view of the plug base, taken along the line Il-Il in Figure 1 (with some detail behind the section plane omitted); Figure 3 is a partial sectional view taken along the line Ill-Ill in Figure 1; Figure 4 is a partial sectional view taken along the line lV-IV in Figure 1; Figure 5 is an under-plan view of a cover for the base shown in Figure 1; and Figure 6 is a view, from the cable entry side, of the cover shown in Figure 5; Figure 7 is a plan view of a base of a modified three-pin 13 Amp mains plug; Figure 8 is a sectional view taken along the line 8-8 in Figure 7; Figure 9 is an under-plan view of a cover for the plug base shown in Figure 7; and Figure 10 is a sectional view taken along the line 10-1 0 in Figure 9.

Referring to Figures 1 to 6 of the drawings, a plug base 10 and cover 12 are formed of hard moulded plastics material.

The base 10 is provided with a live pin 1 4L, a neutral pin 1 4N and an earth pin 1 4E, each of brass. Each pin projects from a hole in the base.

Within the thickness of the base 10, four recesses are formed. One of the recesses 16 houses a copper connector strip 1 8 rivetted to the neutral pin 1 4N and extending to a neutral clamp pad 20N.

Another of the recesses 22 houses an earth clamp pad 20E secured by a rivet (not shown) to the earth pin 1 4E. A further recess 24 houses a first fuse clip 26 rivetted to the live pin 1 4L, a cartridge' fuse 28 and a second fuse clip 30 which is rivetted to a copper strip 32 in turn rivetted to a live clamp pad 20L. The fourth recess 34 forms part of a cable entry opening and houses part of a cable gripping arrangement 36 to be described below.

Three straight tunnels 38L, 38E, 38N are formed in the base and extend from the cable entry recess 34 to respectively the live clamp pad 20L, earth clamp pad 20E and neutral clamp pad 20N. Three coloured areas 40 are marked on the base above the tunnels 38L, 38E, 38N, the colourings being brown, green and yellow diagonal stripes and blue, respectively, in accordance with the colour coding standard in the United Kingdom for flexible cables. Four through holes 42 are provided adjacent the corners of the base 10.

The cover 12 fits the base 10 and has four tapped blind holes 44, optionally having threaded brass inserts, which register with the holes 42 in the base. The base 10 and cover 12 are secured together by four screws passing through the holes 42 into screw-threaded engagement with the holes 44. The cover 1 2 also has a cable entry recess 46 which registers with the cable entry recess 34 in the base 1 0. Also, two projections 48, 50 are provided.When the cover 12 is fitted, the projections 48, 50 abut respectively the connector strip 1 8 above the neutral pin 1 4N and the fuse clip 26 to prevent axial movement of the neutral and live pins 1 4N, I 4L. The cover also has three clamp projections 52L, 52N, 52E which extend towards but stop just short of the clamp pads 20L, 20N, 20E, respectively, when the cover is fitted. Furthermore, the cover has a peripheral bead 53, to assist gripping the plug to withdraw it from a socket.

The clamp pads 20 and clamp projections 52 have complementary serrated surfaces 54 which are closely spaced apart and which provide a zigzag path therebetween when the cover 1 2 is fitted to the base 10. As the cover 1 2 is drawn to the base 10 by the screws, a cable conductor core between one of the pads 20 and its associated projection 52 is squashed and deformed by the serrations and is firmly gripped thereby in good electrical contact with the conductive pad 20. In order that this clamping arrangement may be able to cope better with various sizes of conductor core, it is envisaged that some sort of spring loading may be provided, for example by placing a resilient mat beneath each clamp pad 20. Once the cover 12 is fitted, the earth clamp projection 52E prevents axial movement of the earth pin 14E.

The cable gripping arrangement 36 comprises a pair of resilient nylon vanes 56, one on the cover 12 and the other on the base 10. Each vane 56 extends across the respective recess 34, 46 and is located in slots 58, 60 in the walls of the recess.

The vanes are inclined and arranged such that, when the cover 12 is fitted to the base 10 without a cable extending into the plug, the two vanes 56 abut in a V-configuration pointing towards the centre of the plug. When a cable is present, the vanes 56 are deformed as the cover 12 is drawn towards the base 10 and dig into the cable sheathing to grip the cable firmly. Since the inclination of the slots 58 may cause problems with moulding, the slots 58 may alternatively be upright and the vanes 56 may be non-planar so that the central portions of the vanes 56 are still inclined as shown in the drawings.

Wiring the plug consists simply of removing the plug cover, checking the fuse, cutting away a predetermined length of outer sheath from the cable to be wired, baring the ends of the live, neutral and earth wires equally and twisting them, pushing the wires through the respective tunnels, fitting the cover and tightening the screws. As the screws are thightened, the bare ends of the wires are clamped between the clamping pads 20 and projections 52, the cable sheath is clamped by the vanes 56 and the pins 14 are axially locked.

With this plug, the conductors are not cut to different lengths and are not secured in a separate stage to the conductors in the plug. The colour coding of the tunnels assists in the correct wiring of the plug, and the provision of tunnels leading to separate recesses helps to ensure that stray strands from different wires do not touch each other. Also, the cable is not gripped at the cable entry in a separate stage during wiring of the plug.

In a modification of the plug, the cover 12 is hinged to the base 10 and less than four screws are used. For example, the hinging may be along the edge of the plug adjacent the pads 20, and two screws may be used to either side of the cable entry recess. Alternatively, the hinging may be along the edge of the plug adjacent the cable entry recess and a single screw may be used passing through the cover 12 into screw-engagement with some part of the earthed metal of the plug.

The tunnelled portion of the base may be made as a separate moulding which is then secured to the remainder of the base.

Referring now to Figures 7 to 10, there is shown a modified plug which is similar to the plug described with reference to Figure 1 to 6 except in the following respects.

Firstly, each tunnel 38 has an open top at the entrance to the tunnel nearer the cable grip. Put another way, the entrances to the tunnels 38 are separated by dividing walls 80. The purpose of this feature is to facilitate insertion of the wires into the tunnels whilst still separating the wires.

Secondly, the modified plug is provided with conventional screw-clamping terminals 82. They are, however, arranged in a row at the ends of the tunnels 38. Holes are provided in the terminals 82 in alignment with the tunnels 38 to receive the bare ends of the wires passed through the tunnels prior to clamping the wires with the screws 83.

Thirdly, the cover 1 2 is secured to the base 10 by means of a hook arrangement and screws. The hook arrangement comprises a hook 84 integrally formed at the top of the cover 1 2 and a complementary groove 86 formed in the top of the base 10. Only two of the screw-threaded holes 44 are provided in the base, on either side of the cable entry, with complementary holes 42 being provided in the cover. When fitting the cover 1 2 to the base, first the hook 84 is mated with the groove 86, and then a pair of screws are fitted through the holes 42 into the holes 44 and tightened to draw the cover 1 2 to the base and clamp the cable.

Fourthly, the cable gripping arrangement is modified in the modified plug. A single inclined resilient vane 87 is used, fitted to the cover 12 by means of integral side arms 88 which engage and are bonded in complementary grooves 90 formed in the cover 12. A ridge 92 is formed in the base 1 0 opposite the tip of the vane 87 so that when the cover 12 is fitted the cable is clamped between the ridge 92 and the tip of the vane 87.

Any of these four modifications described with reference to Figures 7 to 10 may be made separately or in combinations to the plug described with reference to Figures 1 to 6.

Claims (13)

1. A device of said type hereinbefore defined, wherein, for each conductor core of the cable, the base is formed with a respective tunnel extending from a location between the cable entry opening and the respective core connection means to a location adjacent the respective core connecting means.

2. A device of said type defined, or as claimed in Claim 1, wherein the device is a 3-pin mains plug, the earth pin being to one side of the base, the cable entry opening being to the opposite side of the base, and the means for drawing and securing together the base and cover comprising a hook or hinge arrangement connecting the cover to the base adjacent the earth pin and a pair of screw fastening arrangements to either side of the cable entry opening for drawing together the base and cover.

3. A device of said type defined or as claimed in any preceding claim, and further including means for gripping the cable adjacent the cable entry opening, the gripping means coinprising a resilient element mounted on the base or cover, or a pair of such elements mounted respectively on the base and cover, and projecting into the cable path, said resilient element or elements being arranged to be distorted as the cover and base are drawn together and to dig into a cable extending into the device to grip the cable.

4. A device as claimed in Claim 3, wherein two such elements are provided one on the cover and the other on the base, said elements in their undistorted state forming generally a Vconfiguration pointing in the direction of the cable entry.

5. A device as claimed in Claim 3, wherein one such element is provided on one of the base and the cover, the other of the base and cover being formed with a rigid ridge opposite the resilient element.

6. A device of said type defined, or as claimed in any preceding claim, for use with cable having standard colour coded cores, wherein the device is likewise colour-coded to indicate which core should be connected to which connecting means.

7. A device as claimed in Claim 6 when dependent on Claim 1, wherein the tunnels are colour coded.

8. A device of the said type defined, or as claimed in any preceding claim, wherein, for each conductor core of the cable, the means for electrically connecting the core to the respective conductor element comprises a complementary pair of clamping areas, one of said areas being conductive and provided on the base, and the other area being provided on the cover, said clamping areas being arranged to be moved together as the cover is drawn towards the base to clamp the conductor core therebetween.

9. A device as claimed in Claim 8, wherein the clamping areas are serrated complementarily.

10. A device as claimed in Claim 8 or 9, wherein at least one of said clamping areas is provided on a clamping element resiliently mounted on the base or cover, as the case may be.

11. A device as claimed in any preceding claim, wherein the core connecting means are substantially equidistant from the cable entry opening.

12. A device as claimed in any preceding claim in the form of a mains plug.

13. An electrical connection device substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 6 or Figures 7 to 10 of the accompanying drawings.